A prior art sterilization system is described in U.S. Pat. No. 3,476,506, issued Nov. 4, 1969. This prior art patent discloses an ampule or source sterilant, a gas release bag which contains the ampule, a liner bag which contains the gas release bag and the items to be sterilized, and a metal container which contains the liner bag. Ethylene oxide sterilizing gas from the ampule is released into the gas release bag and the sterilization gas in the gas release bag is released into the liner bag to sterilize items within the liner bag. After a period of time (e.g. 4 hours), virtually all of the gas that is contained within the ampule is diffused from the inside of the gas release bag into the liner bag where it held in contact with the items to be sterilized for the duration of the sterilizing cycle (e.g. 12 hours). During this time, a significant portion of the gas is gradually released by the liner bag gas diffusion membrane into the space between the liner bag and the metal container, and the gas escapes from the unsealed metal container into the ambient work area.
This gas sterilization system is marketed commercially by H. W. Andersen Products, Inc. under the registered trademark ANPROLENE.RTM. and is disclosed in the aforementioned U.S. Pat. No. 3,476,506, the contents of which are incorporated herein by reference.
One problem with this prior art sterilization system is that the operator is exposed to the sterilizing gas in the work area and to the gas in the liner bag when the latter is opened upon completion of the sterilization cycle. One attempt to overcome this problem is set forth in the present Assignee's U.S. Pat. No. 4,937,046, issued Jun. 26, 1990, entitled "Sterilization System and Method" which discloses utilizing a post-sterilization flush which minimizes the extent of residue sterilant in the surrounding work area.
In another prior art gas sterilizer, described in U.S. Pat. Nos. 3,516,223 and 3,630,665 and marketed commercially by H. W. Andersen Products, Inc. under the registered trademark STERIJET.RTM., the items to be sterilized are prepared by washing and drying in the same manner as for the previously-described sterilization system. These items are then wrapped in paper or cloth and placed in a bag having a permeable membrane. The bag is placed over a spout extending between jaws of a sterilizing device and air is pumped from the bag until the bag appears to be vacuum-tight around the enclosed items. An appropriate dose of sterilizing gas is then injected into the bag.
An impulse of electric current is passed through a heating wire carried on one of the jaws, and the heating wire heats the bag to a temperature sufficient to fuse the bag but below the ignition temperature of the sterilant to thereby form a seal.
The sealed bag containing the items to be sterilized and the sterilizing gas is then placed in a heated and ventilated aerator chamber where it remains for at least 12 hours. By way of example, the aerator chamber may be heated to 50.degree. C. During this time, the gas sterilizes the contents of the bag and then diffuses through the permeable membrane of the bag into the aerator chamber where it is evacuated by a ventilator. Since the material from which the bag is fabricated is permeable to the sterilizing gas and impermeable to air, the vacuum initially provided in the bag reappears as the gaseous sterilant diffuses out of the bag, giving the bag a finished and a characteristic vacuum-tight appearance of a sterile package. A sterilizing system of this type is disclosed in the aforementioned U.S. Pat. Nos. 3,516,223 and 3,630,665, the contents of which are incorporated herein by reference.
Unlike the first system described heretofore, the second system does not use pre-measured, unit doses of ethylene oxide sterilant. Also, the second system is a more expensive system to buy and to maintain than the first system.
It has been widely recognized for many years by those skilled in the art and science of sterilization with gases such as ethylene oxide that the sterilization gas is more effective in killing microorganisms if those microorganisms are normally hydrated and, further, if the sterilization process is carried out in an atmosphere which contains at least 30% relative humidity.